A flat-shaped panel such as an active matrix type liquid crystal panel is frequently used as a display part of an electronic device. The active matrix type liquid crystal panel is a system-on-chip display (system display) in which a display area and a peripheral circuit section that drives the display area are formed integrally on an insulating substrate.
A small-sized electronic device, such as a cellular phone terminal and a PDA (Personal Digital Assistance), that can be switched between a normal power consumption state and a low power consumption state has been developed. There is a technique that has been known in which a display apparatus (system display) performs a so-called partial mode display in response to the low power consumption state when the main body (main set) of the electronic device is switched to the low power consumption state. For example, a liquid crystal panel incorporated into a cellular telephone terminal performs a so-called “standby mode display” in the low power consumption state. More specifically, only the minimum necessary information is displayed (the partial mode display) for purposes of power savings. However, in this partial mode, the display apparatus is substantially in an operating state and, therefore, the power savings cannot be expected so much. To respond to the low power consumption state of the main set in another way, there is proposed a method in which the display apparatus performs a preparation process (an OFF sequence) for shutting off the power supply before turning off the power supply to the display apparatus. In applications requiring suppression of the power consumption of the display apparatus (system display), this power supply shut-off method is adopted. However, in this case, a large capacity switch is required to shut off the power supply from the main set to the system display. As a result, there is a disadvantage in that the number of parts and, thus, the size and cost of the main set will be increased.
In recent years, there has been developed a technique that switches between an operation mode and a waiting mode (standby mode) in response to the switching between the normal power consumption state and the low power consumption state of the main body of the electronic device, as described in Japanese Patent Laid-open No. Hei 07-271323. In the standby mode, while a power supply voltage is supplied from the main set, power consumption of the panel is suppressed by blocking the operation of the system display and inactivating the peripheral circuit section included in the system display. In this standby mode, while the power supply from the main set to the system display is kept active, active power consumption of the system display is suppressed. This eliminates the need for the large capacity switch for turning off the power supply and, therefore, is advantageous in terms of the size and cost of the main set. However, there is still a problem to be solved in that, in the conventional standby mode, there is not a sufficient means for suppressing the active power consumption of the display apparatus, and therefore, sufficient power savings cannot be achieved in the standby mode.